I dont think comparing these sort of states to pure DMT experiences is really realistic. There are a whole range of active indoles of which DMT could be concidered a harmonic of present in human metabolism. Pinoline is something that is rarely talked about. Harmine is basically a pinoline analogue, though harmine is a harmala and pinoline in a tryptoline, both are 6methoxylated beta carbolines. Pinoline is a direct metabolite of melatonin and is at least 2x as powerful I believe. According to some theories pinoline is a precurser for 5meoDMT, who's synthesis in the pineal gland is much more likely from what I have read. Now, correct me if I am wrong, but I believe that both pinoline and harmine have minor action at the NMDA site..and NMDA dissociatives such as ketamine seem to parallel certain aspects of NDE's. There is also a ketamine analogue called agmatine found in the brain.
In reality, it would make much more sense that endogeous OBE's and NDE's etc are due to higher levels of a whole synergistic cocktail of actives. It's just like how DMT is much deeper and more meaningful when harmalas are consumed with it(IMO)..I think ayahuasa as opposed to just vaped DMT is more similar to this sort of stuff. I have had sleep paralysis,OBE's and lucid dreams my entire life and they are much more similar to high doses of harmalas with or without moderate doses of DMT than just smoked DMT alone. I bet that is becasue harmine actaully increases melatonin and pinoline turn over and the saturation of them in the brain which sort of boosts all these endogenous neurotransmitters. I have woken up into full on ayahuasca like experiences in the middle of the night many times without taking anything. It is distinct, very much like oral harmalas and DMT.
I have never had a NDE so I dont really know how similar they are to OBE's and lucid dreams etc. But I would suspect other chemicals are involved besides just DMT alone.
